Re: [PATCH net-next 2/6] page_frag: unify gfp bits for order 3 page allocation

[Yunsheng Lin]

On 2024/1/5 23:35, Alexander H Duyck wrote:
> On Wed, 2024-01-03 at 17:56 +0800, Yunsheng Lin wrote:
>> Currently there seems to be three page frag implementions
>> which all try to allocate order 3 page, if that fails, it
>> then fail back to allocate order 0 page, and each of them
>> all allow order 3 page allocation to fail under certain
>> condition by using specific gfp bits.
>>
>> The gfp bits for order 3 page allocation are different
>> between different implementation, __GFP_NOMEMALLOC is
>> or'd to forbid access to emergency reserves memory for
>> __page_frag_cache_refill(), but it is not or'd in other
>> implementions, __GFP_DIRECT_RECLAIM is masked off to avoid
>> direct reclaim in skb_page_frag_refill(), but it is not
>> masked off in __page_frag_cache_refill().
>>
>> This patch unifies the gfp bits used between different
>> implementions by or'ing __GFP_NOMEMALLOC and masking off
>> __GFP_DIRECT_RECLAIM for order 3 page allocation to avoid
>> possible pressure for mm.
>>
>> Signed-off-by: Yunsheng Lin <linyunsheng@xxxxxxxxxx>
>> CC: Alexander Duyck <alexander.duyck@xxxxxxxxx>
>> ---
>>  drivers/vhost/net.c | 2 +-
>>  mm/page_alloc.c     | 4 ++--
>>  net/core/sock.c     | 2 +-
>>  3 files changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
>> index f2ed7167c848..e574e21cc0ca 100644
>> --- a/drivers/vhost/net.c
>> +++ b/drivers/vhost/net.c
>> @@ -670,7 +670,7 @@ static bool vhost_net_page_frag_refill(struct vhost_net *net, unsigned int sz,
>>  		/* Avoid direct reclaim but allow kswapd to wake */
>>  		pfrag->page = alloc_pages((gfp & ~__GFP_DIRECT_RECLAIM) |
>>  					  __GFP_COMP | __GFP_NOWARN |
>> -					  __GFP_NORETRY,
>> +					  __GFP_NORETRY | __GFP_NOMEMALLOC,
>>  					  SKB_FRAG_PAGE_ORDER);
>>  		if (likely(pfrag->page)) {
>>  			pfrag->size = PAGE_SIZE << SKB_FRAG_PAGE_ORDER;
>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>> index 9a16305cf985..1f0b36dd81b5 100644
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -4693,8 +4693,8 @@ static struct page *__page_frag_cache_refill(struct page_frag_cache *nc,
>>  	gfp_t gfp = gfp_mask;
>>  
>>  #if (PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE)
>> -	gfp_mask |= __GFP_COMP | __GFP_NOWARN | __GFP_NORETRY |
>> -		    __GFP_NOMEMALLOC;
>> +	gfp_mask = (gfp_mask & ~__GFP_DIRECT_RECLAIM) |  __GFP_COMP |
>> +		   __GFP_NOWARN | __GFP_NORETRY | __GFP_NOMEMALLOC;
>>  	page = alloc_pages_node(NUMA_NO_NODE, gfp_mask,
>>  				PAGE_FRAG_CACHE_MAX_ORDER);
>>  	nc->size = page ? PAGE_FRAG_CACHE_MAX_SIZE : PAGE_SIZE;
>> diff --git a/net/core/sock.c b/net/core/sock.c
>> index 446e945f736b..d643332c3ee5 100644
>> --- a/net/core/sock.c
>> +++ b/net/core/sock.c
>> @@ -2900,7 +2900,7 @@ bool skb_page_frag_refill(unsigned int sz, struct page_frag *pfrag, gfp_t gfp)
>>  		/* Avoid direct reclaim but allow kswapd to wake */
>>  		pfrag->page = alloc_pages((gfp & ~__GFP_DIRECT_RECLAIM) |
>>  					  __GFP_COMP | __GFP_NOWARN |
>> -					  __GFP_NORETRY,
>> +					  __GFP_NORETRY | __GFP_NOMEMALLOC,
>>  					  SKB_FRAG_PAGE_ORDER);
>>  		if (likely(pfrag->page)) {
>>  			pfrag->size = PAGE_SIZE << SKB_FRAG_PAGE_ORDER;
> 
> Looks fine to me.
> 
> One thing you may want to consider would be to place this all in an
> inline function that could just consolidate all the code.

Do you think it is possible to further unify the implementations of the
'struct page_frag_cache' and 'struct page_frag', so adding a inline
function for above is unnecessary?

> 
> Reviewed-by: Alexander Duyck <alexanderduyck@xxxxxx>
> 
> .
>